Modelling of the excitation for low-rate speech coding (⩽4 kbit/s)

Research into speech coding at these rates has been very active for several years, with the major objective of ensuring the best possible quality of the reconstructed signal while keeping to a reasonable processing cost, it is estimated that modelling of the production of the speech signal is necessary to achieve this objective at low bit rates. It permits redundancy reduction by estimation of a judiciously chosen set of model parameters. The paper is concerned with excitation modelling in a speech production model of linear predictive coding type (Ann. Telecommun. vol. 46, no.3-4, p.223-39 of 1991), The selection and estimation of representative excitation parameters are of prime importance in ensuring a synthesis of quality. The estimation of voicing and the general synthetic model are presented and developed